// use init replace init at constructor
// disadvantage: must call init manully
function Person() {}
Person.prototype.init = function(name) {
	this.name = name;
};
Person.prototype.getName = function() {
	return this.name;
}

function Employee() {}
Employee.prototype = new Person();
Employee.prototype.constructor = Employee;
Employee.prototype.init = function(name, employeeID) {
	this.name = name;
	this.employeeID = employeeID;
};
Employee.prototype.getEmployeeID = function() {
	return this.employeeID;
};

//
var zhang = new Employee();
zhang.init("ZhangSan", "1234");
console.log(zhang.getName()); // "ZhangSan"
